In general, when semiconductor devices are fabricated on a wafer, reliability testing is performed for semiconductor devices on the wafer using electrical signals applied thereto. In particular, Electrical Die Sorting (EDS) test can be used to test for defects of semiconductor devices on the wafer using direct electrical contacts. A machine for performing an EDS test is called as a wafer probing machine or wafer test equipment.
In a conventional EDS test, an electrical characteristic of a semiconductor is tested by contacting a needle-shaped probe to a surface of a metal pad formed on a semiconductor chip. A probe card needs to be replaced with a new probe card based on a type of a wafer to be tested or the test environment. The probe card also needs to be replaced when the probe card is broken or worn out. In the conventional test equipment, a docking position of a test head must be set up each time the probe card is replaced.
A conventional method of aligning the test head requires repeated operations which, depending on the operator's experience, can be time consuming. Furthermore, it is difficult to set an exact docking position of the test head because a position of the test head deviates from its initial position after the repeated operations.
Therefore, a need exists for wafer test equipment that is capable of setting an exact docking position of the test head, thereby reducing testing errors and increasing production efficiency.